LAUSR

Objectives Reports from national surveys in South Korea and Japan have indicated that the prevalence of periodontal disease is lower in Korea than in Japan. However, these national surveys have not evaluated factors related to periodontal health condition, including diabetes and metabolic syndrome. This study compared periodontal conditions between Korean and Japanese adults, in the context of general health status. Design Cross-sectional study. Setting National survey in South Korea (Korean National Health and Nutrition Examination Survey, ‘KNHANES’) and a population-based study in Japan (Hisayama study); both were conducted in 2012. Participants This study included 3574 Korean and 2205 Japanese adults aged 40–79 years. Outcome measures Periodontal condition was assessed by using the Community Periodontal Index (CPI). Examiners in Japan underwent clinical calibration training for periodontal examination with a gold-standard examiner from KNHANES, prior to the Hisayama study. Results The age-adjusted prevalences of periodontal disease, defined as CPI score ≥3, were 31.4% and 42.1% in South Korea and Japan, respectively (p<0.001). The age-adjusted prevalences of diabetes (p=0.018) and metabolic syndrome (p=0.001) were higher in Korea than in Japan. The numbers of present and filled teeth and percentages of participants who visited a dental clinic in the last 12 months were higher in Japan than in Korea (all p<0.001). Logistic regression analysis showed that the Japanese participants were more likely to have periodontal disease than were the Korean participants, after adjusting for age, sex, occupation, oral health status, oral health behaviour, diabetes and metabolic syndrome. Conclusions A higher prevalence of periodontal disease was found in Japanese participants than in Korean participants. Further studies are needed to more clearly elucidate factors underlying the difference in periodontal conditions between the two populations, including those related to the dental healthcare system and dietary intake.